Photoinstability Of Different Substance Groups Of Antimycotics

Imidazole derivatives

Bilbnazol Clotrimazol Econazol Fluconazol Isoconazol Ketoconazole Miconazol Oxiconazol Terconazole Tioconazol

Polyene derivatives

Amphotericin B Natamycin Nystatin other agents

Griseofulvin Naftifin Sulbentin Tolnaftat

100%

Figure 6 Photoinstability of antimycotics in methanolic solution (2 mg/100 ml)with UV-filter

100%

Figure 6 Photoinstability of antimycotics in methanolic solution (2 mg/100 ml)with UV-filter

The photostability tests have been carried out with the Suntest CPS.6 This light testing cabinet is equipped with a xenon lamp as light source. To adopt its spectrum to that of natural sunlight a UV filter is set in. By these means the unnatural UV range below 290 nm can be eliminated (Figure 5).

In Figure 6 of the photoinstability testing results of the various antimycotics in this work are compared: The black bars symbolise the residual drug content after 2 h irradiation in a methanolic solution. The HPLC methods are described.7'8'9'10

The azolantimycotics show no uniform behaviour to irradiation. 4 out of 10 investigated imidazole derivatives are photostable like clotrimazol, 4 of them are photolytically degraded only to 1-3% like tioconazole. However, ketoconazole and terconazole are completely destroyed after this light stressing,7 (Figures 7 and 8).

The polyenantibiotics are a very light sensitive substance group. Amphotericin B, nata-mycin and nystatin were completely degraded after 2 h of irradiation.8

Other antifungal agents show strong differences of their photostability, varying from 5% photodecomposition of tolnaftate to 85% degradation of naftifine. Griseofulvin with a loss of about 47 % and sulbentine with about 30 % show significant photodegradation, too.9'10

Figure 7 Photodegradation of 6 azolantimycotics(2 mg/100 ml in methanolic solution, Suntest CPS, UV-filter). Bifonazol -X- , Fluconazol o , Clotrimazol -at- , Isoco-nazol -Q- , Econazolnitrat , Miconazol -x- .

time (min)

Figure 7 Photodegradation of 6 azolantimycotics(2 mg/100 ml in methanolic solution, Suntest CPS, UV-filter). Bifonazol -X- , Fluconazol o , Clotrimazol -at- , Isoco-nazol -Q- , Econazolnitrat , Miconazol -x- .

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